(1) Field of the Invention
The present invention relates to a fixed or slide-type constant velocity universal joint used in a power transmission system in automobiles and various industrial machineries. The fixed-type or slide-type constant velocity universal joint is mounted on a drive shaft or a propeller shaft used in, for example, a front-engine, front-wheel drive (FF) vehicle, a four-wheel drive (4WD) vehicle, and a front-engine, rear-wheel drive (FR) vehicle.
(2) Description of Related Art
A drive shaft of an automobile has a configuration in which a slide-type constant velocity universal joint is mounted on one axial end of the shaft and a fixed constant velocity universal joint is mounted on another axial end.
A tripod constant velocity universal joint (TJ) that is a slide-type constant velocity universal joint used as a connecting joint of the drive shaft includes an outer joint component (outer member), an inner joint component (tripod member), and a rolling element (roller) as main components. In the outer joint component, three track grooves are formed on an inner circumferential surface in an axial direction, and a roller guiding surface is provided in the axial direction on both sides of each track groove. The inner joint component includes three leg shafts projecting in a radial direction. The rolling element is housed between the leg shafts of the inner joint component and the roller guiding surfaces of the outer joint component so as to rotate freely.
A Birfield constant velocity universal joint (BJ) that is a fixed constant velocity universal joint includes an outer joint component (outer member), an inner joint component (inner member), a plurality of balls, and a cage as main components. In the outer joint component, a plurality of track grooves are formed on an inner spherical surface along an axial direction, the track grooves being equal distances apart in a circumferential direction. In the inner joint component, a plurality of track grooves forming pairs with the track grooves on the outer joint component are formed on an outer spherical surface along the axial direction, the track grooves being equal distances apart in a circumferential direction. The plurality of balls that transmit torque are interposed between the track grooves on the outer joint component and the track grooves on the inner joint component. A cage that holds the balls is interposed between the inner spherical surface of the outer joint component and the outer spherical surface of the inner joint component.
A configuration in which an axial end outer diameter of the shaft is pressed into an axis hole inner diameter of the inner joint component is used as a connection configuration between the slide-type constant velocity universal joint or the fixed constant velocity universal joint, and the shaft. A female spline is formed on the axis hole inner diameter of the inner joint component as a recess and a projection running along the axial direction, and a male spline is formed on the axial end outer diameter of the shaft.
A hardening process by, for example, induction hardening or carburizing and quenching is performed on the axis hole inner diameter of the inner joint component on which the female spline is formed and on the axial end outer diameter of the shaft on which the male spline is formed, thereby forming hardened layers. Strength of the axis hole inner diameter of the inner joint component and the axial end outer diameter of the shaft is ensured by the hardened layers being formed.
The axial end outer diameter of the shaft is pressed into the axis hole inner diameter of the inner joint component, and the male spline and the female spline mesh. As a result, the shaft is fitted into the inner joint component. As a result of spline engagement between the shaft and the inner joint component, torque can be transmitted therebetween (refer to, for example, FIG. 2 in Patent Document 1, Japanese Patent Laid-Open Publication No. 2003-314580).
In a connection configuration between the inner joint component and the shaft such as this, there is a configuration in which a stopper ring with a round cross-section attached to the axial end of the shaft comes into contact with a locking surface provided on the inner joint component, thereby serving as a dislocation stopper (refer to, for example, Patent Document 2, Japanese Patent Laid-Open Publication No. Heisei 8-68426).    Patent Document 1: Japanese Patent Laid-Open Publication No. 2003-314580    Patent Document 2: Japanese Patent Laid-Open Publication No. Heisei 8-68426